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Neuroscience > Histology of the Central Nervous System > Flashcards

Histology of the Central Nervous System Flashcards

1
Q

cells that respond to stimuli through electrochemical mechanisms
- Excitable or inhibitory

A

Neurons

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2
Q

support cells involved in conduction speed, repair, neurotransmitter maintenance

A

Glia

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3
Q

dense network of interwoven nerve fibers &

their branches and synapses, together with glial filaments

A

Neuropil

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4
Q

Anatomy of a Neuron

A
  • Cell body with nissl substance/bodies
  • Dendrites with dendritic spines
  • Long axon covered by myelin that emerges from an axon hillock
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5
Q

The Axon

- site where excitatory or inhibitory stimuli are initiated

A

Initial segment

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6
Q

The Axon
• distal end of the axon
- some have branching, collateral branches

A

Terminal arborization

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7
Q

The Axon

  • small ends of axons
  • Dilation of branch ends & contact postsynaptic cell
A

Telodendria

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8
Q

Structural Classification of Neurons

  • most common, throughout CNS
  • MNs, CNS interneurons
A

Multipolar

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9
Q

Structural Classification of Neurons
- sensory neurons of the retina, olfactory mucosa,
and inner ear

A

Bipolar

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10
Q

Structural Classification of Neurons

- other sensory neurons, including the dorsal root ganglia & cranial ganglia

A

Uni/Pseudounipolar

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11
Q

Structural Classification of Neurons
- neurons of the CNS lack true axons and do not
produce action potentials, but regulate local electrical
changes of adjacent neurons

A

Anaxonic

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12
Q

– Carries material from the nerve cell body to the periphery
– Utilizes kinesin, microtubule-associated motor protein that uses ATP

A

Anterograde transport

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13
Q

– Carries material from the axon terminal & dendrites to the nerve cell body
– Utilizes dynein, microtubule-associated motor protein

A

Retrograde transport

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14
Q

conveys substances from the cell body to the terminal bouton at the speed of 0.2 to 4 mm/day

  • Anterograde only
  • Tubulin molecules, actin molecules, & neurofilament proteins
A

Slow Transport

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15
Q

Conveys substances in both directions at a rate of 20 to 400 mm/day

  • Anterograde carries membrane-limited organelles, sER components, synaptic vesicles, & mitochondria
  • Retrograde carries membrane-limited organelles & molecules endocytosed at the axon terminal; path followed by toxins & viruses
A

Fast transport

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16
Q

Functional Classification of Neurons
- (afferent) receive stimuli from receptors throughout
the body

A

Sensory neurons

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17
Q

Functional Classification of Neurons

- (efferent) send impulses to effector organs

A

Motor neurons

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18
Q

Functional Classification of Neurons

- neurons under voluntary control & innervate skeletal muscle (motor neurons)

A

Somatic

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19
Q

Functional Classification of Neurons

- control the involuntary or unconscious activities of glands, cardiac muscle, & smooth muscle

A

Autonomic

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20
Q

Functional Classification of Neurons

  • establish relationships among other neurons, forming complex functional circuits
  • Comprise 99% of all neurons in adults
A

Interneurons

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21
Q
  • Presynaptic terminal bouton contains mitochondria & synaptic vesicles → release NT via exocytosis
  • 20- to 30-nm-wide intercellular space, synaptic cleft separates pre- & postsynaptic membranes
  • Postsynaptic cell membrane contains:
  • Receptors for the neurotransmitter
  • Ion channels to initiate a new impulse
A

Chemical Synapse

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22
Q

• Permit direct, passive flow of electrical current from one neuron
to another
- Potential difference generated locally
by presynaptic action potential

• Current flow occurs via gap junctions, link pre- & postsynaptic membranes (2nm)

• Contain connexon proteins, permit
diffusion of small molecules &
electric current flow (NO vesicles)

A

Electrical Synapse

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23
Q

fibrous intercellular network of cellular processes emerging from neurons & glial cells

A

Neuropil

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24
Q
  • Large number of long, branching processes

* Proximal regions are reinforced with intermediate filaments made of glial fibrillary acid protein (GFAP)

A

Astrocytes

25
Q

• Processes can affect the formation, function, and plasticity of synapses

• Regulate extracellular ionic concentrations around neurons, with
particular importance in buffering extracellular ?levels

• Guide and physically support movements & locations of
differentiating neurons during CNS development

• Extend fibrous processes with expanded ? that cover capillary endothelial cells and modulate blood flow and help move nutrients, wastes, and other metabolites between neurons and capillaries

• Filling tissue defects after CNS injury by proliferation to form an
?

A

Astrocyte Functions

  • K+
  • perivascular feet
  • astrocytic scar
26
Q

• Extend many processes that wrap repeatedly around a portion of a nearby axon
- Cytoplasm gradually moves out, leaving compacted layers of cell
membrane, myelin

• Will enwrap axons from multiple neurons

• Usually appear as small cells with
rounded, condensed nuclei & unstained
cytoplasm

A

Oligodendrocytes

27
Q

• Glial cells derived from
neuroepithelium
• Begins in lower brain stem, older tracts first
• 6th months through puberty

A

CNS: oligodendrocytes

28
Q

• NCC derived
• Motor roots myelinated
before sensory roots
• 4th month

A

PNS: Schwann cells

29
Q

• ? cells that line
the fluid-filled ventricles of the brain &
the central canal of the spinal cord

• Apical end may have cilia & long microvilli

  • Facilitate movement of CSF
  • Likely involved in absorption

• Joined apically by apical junctional complexes & there is no ?

A

Ependymal Cells

  • Columnar or cuboidal
  • basal lamina
30
Q

• Elaborately folded & highly vascular tissue,
found in the roofs of the ?, & in parts of ?

• Contains a thin layer of well-vascularized pia
mater covered by ? ependymal cells

• Removes H2O from blood & releases it as
CSF
– Contains ?, ?, & ? ions 
– Very little protein
 – Only cells include sparse lymphocytes
  • Completely fills ventricles, central canal of SC, subarachnoid & perivascular spaces
  • ? provide absorption pathway for CSF back into the venous circulation
A

Choroid Plexus

  • 3rd & 4th ventricles
  • lateral ventricular walls
  • columnar to cuboidal
  • Na+, K+, & Cl-
  • Arachnoid villi
31
Q

• Less numerous than oligodendrocytes or
astrocytes

• Migratory, will remove damaged or unactive synapses or other fibrous
components

• Major mechanism of immune defense in
the CNS, removing any microbial invaders

• Originate from monocytes

A

Microglia

32
Q

Cerebellar Cortex

- has much neuropil & scattered neuronal cell bodies

A

Molecular Layer

33
Q

Cerebellar Cortex

  • extend dendrites throughout the molecular layer as a branching basket of nerve fibers
  • Conspicuous in H&E-stained sections
A

Purkinje Cells

34
Q

Cerebellar Cortex
- contains various very small, densely packed neurons (i.e., granule cells)
& little neuropil

A

Granular layer

35
Q

Cerebellar Cortex

- Organized into folia with the ? located deep

A

cerebellar medulla

36
Q

Cerebral Cortex

- Biologically older parts of the cortex are arranged into three layers

A

Archicortex

37
Q

Cerebral Cortex

  • Most of the cortex (~90%)
  • Consists of 6 layers
A

Neocortex

38
Q

Cerebral Cortex
- pyramid-shaped cell bodies with the apex directed towards the
cortical surface
- Huge upper motor neurons of the motor cortex (Betz cells), are the largest of these cells

A

Pyramidal Cells

39
Q

Cerebral Cortex

- small neurons with a cell body the shape of a star (look like granules in micrographs)

A

Granule (stellate) cells

40
Q

Cerebral Cortex

- Small polygonal cells with a few short dendrites

A

Cells of Martinotti

41
Q

Cerebral Cortex
- Spindle-shaped cells oriented at right angles to the surface of the
cerebral cortex

A

Fusiform cells

42
Q

Cerebral Cortex

- small & spindle-shaped but oriented parallel to the surface (least common)

A

Horizontal cells of Cajal

43
Q

Cortical Layers
- consists largely of fibers, most of which travel parallel to the surface, & mostly neuroglial cells & horizontal cells of Cajal

A

Plexiform Layer (or molecular layer)

44
Q

Cortical Layers

- consists mainly of small pyramidal cells & granule cells

A

Small Pyramidal Cell Layer (or outer granular layer)

45
Q

Cortical Layers

- pyramidal cells are somewhat larger and possess a typical pyramidal shape; not sharply demarcated from layer II

A

Layer of Medium Pyramidal Cells (or layer of outer pyramidal cells)

46
Q

Cortical Layers

- is characterized by the presence of many small granule cells

A

Granular Layer (or inner granular layer)

47
Q

Cortical Layers

- contains pyramidal cells are extremely large (Betz cells) in motor areas

A

Large Pyramidal Cell Layer (or inner layer of pyramidal cells)

48
Q

Cortical Layers

- contains cells with diverse shapes, many are fusiform cells

A

Polymorphic Layer

49
Q

• Function in the “limbic system“

• Integrates inputs various cortical areas into complicated behaviors
- Learning, memory, & social interaction

• Morphologically is considered ?,
- Comprised of three layers (rather the six layers found in the cerebral cortex)

A

The Hippocampus & Dentate Gyrus

  • archicortex
50
Q

Hippocampus Layer:

- nerve fibers & small cell bodies of interneurons

A

Polymorphic layer

51
Q

Hippocampus Layer:

- hippocampal pyramidal cells

A

Middle pyramidal cell layer

52
Q

Hippocampus Layer:

- Dendrites of the pyramidal cells

A

Molecular layer

53
Q

Dentate gyrus Layer:

- Nerve fibers (known as “mossy fibers”) & cell bodies of interneurons

A

Polymorphic layer

54
Q

Dentate gyrus Layer:

- Round, neuronal cell bodies of dentate granule cells

A

Middle granule cell layer

55
Q

Dentate gyrus Layer:

- Containing dendrites of the granule cells

A

Molecular Layer

56
Q

The region where the head of hippocampus abuts the dentate gyrus

A

hilus

57
Q

• Most common neurodegenerative disease,
incidence increases with age
- Typical presentation is 70+ years

• Symptoms:
- Memory failure, progressing steadily to involve motor skills, speech & sensation

• Etiology is unknown, small proportion of
cases have a genetic association

• Striking thinning of gyri, particularly those
of the ? and ? lobes

A

Alzheimer’s disease

  • frontal and temporal
58
Q

Alzheimer’s disease
- amorphous, pink
masses in the cortex

A

Amyloid (amyloid β) plaques

59
Q

Alzheimer’s disease

- flame-shaped skeins formed by abnormal accumulation of tau

A

Neurofibrillary tangles

Neuroscience (14 decks)

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